1. Field of the Invention
The present invention relates to an image forming apparatus such as a page printer and an electrophotographic copying machine using a electrophotographic process.
2. Description of the Related Art
In a conventional electrophotographic process used in an image forming apparatus such as an electrophotographic copying machine and a page printer, a photosensitive body serving as a photoelectric converter for converting an optical image into an electrostatic image is used. After the photosensitive body is precharged (formation of charges) by a corona charger or the like the photosensitive body is exposed by the optical image to form the electrostatic latent image. The charges of the exposed portion are neutralized and disappear by the photoconductive effect of the photosensitive body. Charges are maintained in a non-exposed portion. In this manner, the optical image is converted into a charge image The charge image is developed by a toner to form a visible toner image, and this toner image is transferred and fixed on a recording medium. However, when the photosensitive body is precharged by the corona charger, ozone is produced.
Since the above electrophotographic process is featured by its high speed and high image quality, and will satisfy requests such as high image quality, high speed, and low running cost which are demanded to a hard copying machine, the electrophotographic process will be continuously used as a dominant recording scheme of the hard copying machine.
However, in recent years, as a large number of copying machines and page printers are popularly used in offices, these machines adversely affect the environments of the offices to pose a problem. More specifically, in consideration of the influence of ozone to human bodies, the production and leakage of ozone from the machines are being strictly regulated and legislated.
The environmental problem will continuously be a serious problem in the future, the regulation of ozone is increasingly strict, and a reduction of ozone is expected.
Strong demand has arisen for an image forming apparatus using an electrophotographic process serving as a recording process which does not use the corona charger.
In conventional exposure to form an electrostatic latent image, since the uniformly precharged surface of a photosensitive body is scanned with a beam to form the latent image, positional errors of optical beam scan appear as positional errors of the pixels of the formed image. For example, the rotational speed of a photosensitive drum must be very accurately adjusted so as to minimize the positional errors. This is a factor of increasing the cost of the image forming apparatus.